Trolls are named after the first thing they eat, so Pee Hat probably ate a Partyhat, an item often referred to as a "Phat".

A good strategy to kill them is to stand 2 steps south of the entrance, and kill one after the other. the only problem with this is that when you go to pick up your drop from Pee Hat you will be attacked by several thrower trolls.

Universal drops

Trivia

The name "Pee Hat" is a reference to Partyhats, which are colloquially known by players as "P-hats". Since Trolls are named after the first thing they try to eat, Pee Hat is likely to have eaten a partyhat. There is also a chance the troll ate a Pea hat.

Together with Kraka standing next to him, they refer to the extremely expensive Christmas cracker, which gives a Party Hat.